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Session 40 Martin Li

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  • 1. Användning av andraderivator av Spårlägesparameterar för Värdering av Spårlägeskvaliten Martin Li Trafikverket, Underhåll / Ban o vägssystem / Spårsystem 78189, Borlänge, Sweden Transportforum 2012, 11-12 januari I Linköping1 2012-01-10
  • 2. On the Use of Second-Order Derivatives of Track Irregularity for Assessing Track Geometry Quality Martin Li1 , Ingemar Persson2 , Jan Spännar1 and Mats Berg3 1. Swedish Transport Administration (Trafikverket), Borlänge, Sweden 2. AB DEsolver, Optand, Sweden 3. KTH, Rail Vehicles, Stockholm, Sweden 22nd IAVSD Symposium 14-19 August 2011 Manchester, UK The paper has been reviewed and accepted for publication on the journal Vehivle system Dynamics (VSD)2 2012-01-10
  • 3. Background • Measuring and assessing track geometry quality play an important role for safety control and track maintenance. • By using a modern track recording car (TRC), track geometry data including longitudinal level, alignment, gauge, cross level and twist, are routinely collected and assessed. • Current standards and assessment methods are based on the track geometry data alone, by comparing isolated defects with predefined limit values and by computing their standard deviations • But it is the dynamic responses of vehicle and track that are relevant to safety, maintenance costs and ride comfort.3 2012-01-10
  • 4. Track recording car (TRC) in Sweden STRIX Infranord SWE owns 1 pcs. principal Track record. veh. at TRV. New Track record. veh. is planned for 2010 (IMV 200 Infranord) delayed until 2011/12?4 2012-01-10
  • 5. TRV Limit Values (BVF 587.02)5 2012-01-10
  • 6. On-track test results: low correlation between Q-force and LL [5] T. Karis, Track Irregularities for High-Speed Trains, Master Thesis, KTH, 20096 2012-01-10
  • 7. Not easy to detect Alert! > 9 mm Short waved irregularity No forces…. High forces !!7 2012-01-10
  • 8. Motivations of using the derivatives of longitudinal level (LL2) • Only using amplitudes of isolated defects and standard deviations is neither sufficient for vehicle dynamics nor efficient for track maintenance • Without taking into account wavelength and defect shape, the correlation between amplitudes of isolated defects and wheel-rail force is low • Enhanced assessment can be made by Vehicle Response Analysis (VRA), e.g., Pupil by ProRail and VRA-method by DB. However, we observe: – VRA method tends to be very expensive and complex to use – Difficult to consider all vehicle types and all speed ranges – Most importantly, although the VRA-results are good, eventually, it is the track sections and defects that need to be inspected and identified so that appropriate correction maintenance can be taken. • Question: are the derivatives of track defects (LL2) useful?8 2012-01-10
  • 9. Theoretical study: SDOF model The dynamic equation can be written as Transfer function from LL to z The wheel-rail contact force can be calculated as Note: it is LL2 not LL that contributes directly to the dynamic force due to unsprung mass.9 2012-01-10
  • 10. Gensys simulation results LL LL2 Q_dyn • A modified regional passenger train • Vehicle model has been developed and verified by the Green train project at KTH [12] • Speed: V= 220 km/h10 2012-01-10
  • 11. Gensys simulation results:• The correlation coefficient for Q_dyn – LL is only 0.17• The correlation coefficient for Q_dyn – LL2 is increased to 0.63 11 2012-01-10
  • 12. Simulation results for three theoretical track defects (A) Single cosine, 10 m wavelength, ballast settlement (B) Sinusoidal and triangle, standard defect in S&Cs ([8]) (C) Harmonic function, 3 m wavelength, initial rail defect • Same amplitude: 4 mm • Different wavelength and shape • Different second-order derivatives • Different dynamic track forces12 2012-01-10
  • 13. Summary • Current methods of assessing track geometry quality based on amplitudes of isolated defects and standard deviations are neither effective for planning track maintenance nor sufficient for evaluating vehicle dynamics • Theoretical study, simulation results and PSD analysis in this study demonstrate that the second-order derivatives of longitudinal level (LL2) can be used to enhance the assessment of vertical track geometry quality. • Advantages of using LL2: – wavelength and shape of track defects are considered – easy to use. • LL2 cannot and shall not replace the Vehicle Response Analysis (VRA) – When VRA is available, LL2 is useful to further characterise the track defect type – When VRA is not available, LL2 provides an effective analysis of track defects that potentially may result in severe vehicle responses13 2012-01-10
  • 14. ‘Good’: normal track ’Bad’ : track shifted after a test run Both amplitude and 2nd derivatives are big! Thank you for your attention!14 2012-01-10

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